The invention relates to an electrical element of construction having at least one circuit component consisting of a solid ionic conductor, especially in ionically conductive solid electrolyte.
Said ionic conductors and ionically conductive solid electrolytes carry the electrical current substantially by means of ions. In addition to the ionic transport associated with a mass transport corresponding to Faraday's Law, however, electronic currents also flow in the solid ionic conductors and solid electrolytes. The contribution of ionic conduction and of electronic conduction to the total conductivity of the substance is characterized by the transference number, which is the ratio of the partial conductivity of the kinds of particles involved in the conduction of current to the total conductivity. In the case of solid, mixed ionic conductors, the transference number of the ionic conduction is substantially greater than the transference number of the electronic conduction.
Solid electrolytes are used as substitutes for liquid electrolytes in electrochemical energy storage and as electrolytes in galvanic measuring cells for the determination of thermodynamic and kinetic information on chemical reactions (G. Holzapfel and H. Rickert, "High Ionic Conductivity in Solids--Theoretical Aspects and Application," Festkorperprobleme XV, 1975, pp. 317 to 349, Verlag Pergamon, Vieweg, and A. F. Bogenschutz, W. Krusemark, "Elektrochemische Bauelemente," pp. 18, 19 and 41 to 46, 1976, Verlag Chemie, Weinheim). The surface of the ionic conductor and of the solid electrolyte is commonly contacted by two electronically conductive electrodes spaced apart from one another, one of which ionizes the corresponding atoms or molecules and yields the ions to the ionic conductor or solid electrolyte, and the other discharges the ions. While the ions migrate through the ionic conductor or solid electrolyte, as the case may be, the electron transport is accomplished through a circuit between the electrodes. The atoms or molecules to be ionized can originate, for example, from the material substance of the electrodes, as is the case, for example, in electrochemical energy storage (batteries), but they can also be supplied from without through porous electrodes, as is the case, for example, in measuring probes.
In most applications, the ionic conductivity is to be as great as possible, while the electronic conductivity is to be negligible. Although a series of solid ionic conductors and solid electrolytes has become known, the above conditions are more or less well fulfilled by only a few substances. In particular, the number of solid electrolytes having technically practical properties is still very small. Examples of technically practical solid electrolytes are AgI, RbAg.sub.4 I.sub.5, .beta.-aluminum oxide (.beta.-Na.sub.2 O.11Al.sub.2 O.sub.3), doped ZrO.sub.2 and CaF.sub.2. On the other hand, a large number of mixed ionic conductors have become known which have very limited usefulness on account of the high transference number of the electronic conduction.